On Wed, Feb 27, 2013 at 2:02 AM, Akshay Saraswat akshay.s@samsung.com wrote:
timer_get_us returns the time in microseconds since a certain reference point of history. However, it does not guarantee to return an accurate time after a long period; instead, it wraps around (that is, the reference point is reset to some other point of history) after some periods. The frequency of wrapping around is about an hour (or 2^32 microseconds).
TEST=sf probe 1:0; time sf read 40008000 0 1000 Try with different numbers of bytes and see that sane values are obtained
Signed-off-by: Che-Liang Chiou clchiou@chromium.org Signed-off-by: Akshay Saraswat akshay.s@samsung.com
Acked-by: Simon Glass sjg@chromium.org
arch/arm/cpu/armv7/s5p-common/timer.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c index c48a297..de61405 100644 --- a/arch/arm/cpu/armv7/s5p-common/timer.c +++ b/arch/arm/cpu/armv7/s5p-common/timer.c @@ -90,6 +90,21 @@ unsigned long get_timer(unsigned long base) return gd->arch.timer_reset_value / 1000 - base; }
+unsigned long timer_get_us(void) +{
static unsigned long base_time_us;struct s5p_timer *const timer =(struct s5p_timer *)samsung_get_base_timer();unsigned long now_downward_us = readl(&timer->tcnto4);if (!base_time_us)base_time_us = now_downward_us;/* Note that this timer counts downward. */return base_time_us - now_downward_us;+}
/* delay x useconds */ void __udelay(unsigned long usec) { -- 1.8.0